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At least 19 recordsLinked to original sources
PubMed1990

[Forensic efficiency of some highly polymorphic single locus systems].

The single locus probes MS 1, MS 8, MS 31 and MS 43 were investigated in combination with the restriction enzyme HINF I. The frequency distribution of fragment sizes detected by the polymorphic probe MS 8 was plotted for individuals from the Münster area and compared with an English survey. Clear discrepancies were found. The heterozygosity for the four systems was calculated and compared to the English figures. Only MS 8 showed a significant difference.

Alleles↗
PubMed1992

Adequacy of single-locus approximations for linkage analyses of oligogenic traits.

When a disease is controlled by two or more mendelian loci acting epistatically, it can be modeled in a linkage analysis as a single-locus mendelian disease with reduced penetrance. However, the reliability of such an approximation has not yet been demonstrated. This study evaluates the adequacy of such single-locus approximations, when the disease under investigation is determined by two loci, one of which is tightly linked to a genetic marker. A wide range of two-locus models were simulated, and analyzed under both the correct two-locus model and under a single-locus approximation to that model. In general, the single-locus approximations yielded lod scores very close to the correct ones, but estimates of theta tended to be upwardly biased. We conclude that a single-locus linkage analysis will, in general, provide an excellent approximation to a correct (two-locus) linkage analysis of epistatic two-locus diseases. This enables researchers to continue to use single-locus linkage analyses when two-locus disease transmission is a possibility, and it validates linkage findings already obtained under single-locus analysis, even if the disease under investigation proves ultimately to be governed by two mendelian loci. We also examine alternative methods for obtaining parameter estimates for the single-locus approximations, and we discuss both generalizations and limitations of our findings.

Chromosome Mapping↗
PubMed1975

Diabetes mellitus: discrimination between single locus and multifactorial models of inheritance.

Family data from 6,559 diabetic propositi were analyzed using the method of complex segregation analysis in an attempt to discriminate the two models of two-allele single-locus inheritance and multifactorial inheritance for early, middle, and late onset diabetes. The three parameters in the single locus model were: degree of dominance, penetrance, and proportion of phenocopies. In early onset diabetes, the heritability estimated from the multifactorial model was so high as to inidcate major gene action. In middle and late onset diabetes, best fitting single-locus models were found to explain the data as well as the multifactorial model.

Adolescent↗
PubMed1992

The effect of population subdivision on estimates of the likelihood ratio in criminal cases using single-locus DNA probes.

The interpretation of single-locus DNA profile evidence in criminal cases in normally performed using an assumption of independence of frequencies of alleles at different loci. The critical parameter is the probability of a suspect matching a criminal's DNA profile by change. Many authors have been concerned that the assumption of linkage equilibrium may be inaccurate and that the strength of evidence against suspects may be thereby exaggerated. Some have calculated the maximum size of this effect. What matters, however, is not the upper bound of what the true probability might be, but what the actual probability is in a subdivided population. By calculating this, one can show that the effect of population subdivision on the strength of DNA profile evidence is very minor.

Alleles↗
PubMed2025

A single-locus quantitative genetic model incorporating DNA methylation.

We describe a single-locus quantitative genetic model that incorporates effects due to DNA methylation. Extending Fisher's decomposition of the genotypic value, we distinguish two quantities to predict an individual's phenotypic or genetic values: the "basic genetic value" and the "expressed genetic value". We show how these quantities relate to the concept of breeding value and derive their corresponding formulas, along with those for phenotypic variance and covariance between relatives. The resulting parameters are influenced by several factors, including the population distribution of DNA methylation levels, the functional relationship between methylation and phenotype, the magnitudes of genetic and methylation effects, and allele frequencies. We show that under the conditions modeled, the presence of DNA methylation does not bias estimated breeding values.

DNA Methylation↗
PubMed1979

Analysis of inherited epilepsy using single locus mutations in mice.

The neurological expression of mutations at defined gene loci in isogenic mice provides a singular opportunity to investigate the developmental pathophysiology of inherited central nervous system (CNS) diseases. Analysis of the single locus mutants that are currently available shows that CNS diseases that include spontaneous seizures as symptoms can be inherited as simple recessive traits. Mutant gene dose is highly correlated with the spontaneous occurrence of seizures. Single gene defects at one of multiple chromosomal loci may give rise to similar epileptic patterns. One mutation, tottering (tg, chromosome 8, recessive) produces in young mice a focal motor seizure pattern with a somatotopic progression, and behavioral absence seizures accompanied by abnormal bursts of bilaterally synchronous, spike-wave discharges in the electrocorticogram. Spontaneous electrographic and clinical seizures of this general pattern bear close resemblance to common forms of human epilepsy. Defined alterations in restricted neuronal pathways of the mouse brain produced by single locus mutations can be used to infer general principles of inherited epileptogenesis, and may provide specific biological test systems for the development of more selective chemical antagonists of seizure activity.

Animals↗
PubMed1977

Statistical studies on protein polymorphism in natural populations. I. Distribution of single locus heterozygosity.

Surveying the literature, the frequency distribution of single-locus heterozygosity among protein loci was examined in 95 vertebrate and 34 invertebrate species with the aim of testing the validity of the mutation-drift hypothesis. This distribution did not differ significantly from that expected under the mutation-drift hypothesis for any of the species examined when tested by the Kolmogorov-Smirnov goodness-of-fit statistic. The agreement between the observed interlocus variance of heterozygosity and its theoretical expectation was also satisfactory. There was an indication that variation in the mutation rate among loci inflates the interlocus variance of heterozygosity. The variance of heterozygosity for a homologous locus among different species was also studied. This variance generally agreed with the theoretical value very well, though in some groups of Drosophila species there was a significant discrepancy. The observed relationship between average heterozygosity and the proportion of polymorphic loci was in good agreement with the theoretical relationship. It was concluded that, with respect to the pattern of distribution of heterozygosity, the majority of data on protein polymorphisms are consistent with the mutation-drift hypothesis. After examining alternative possible explanations involving selection, it was concluded that the present data cannot be explained adequately without considering a large effect of random genetic drift, whether there is selection or not.

Animals↗
PubMedDate not supplied

Report of a European collaborative exercise comparing DNA typing results using a single locus VNTR probe.

A collaborative exercise was carried out in 1989 among 12 European forensic laboratories using the single locus VNTR probe pYNH24, the restriction enzyme HinfI, the same set of human genomic DNA samples, and a standardized DNA size marker. The objectives of the exercise were: (1) to study the degree of variation within and between laboratories, (2) to obtain information on requirements for technical standardization allowing the exchange of typing results and (3) to compare different approaches for the identification of allelic DNA fragments of unknown size. Each laboratory carried out up to 10 independent typing experiments using the same DNA samples. The results were analysed independently by two laboratories using three different methods. The results of the exercise demonstrate the correlation of typing that can be achieved within and between laboratories under conditions of minimal standardization.

Alleles↗
PubMed1991

Individual identification by VNTR analysis using minisatellite DNA probe to distinguish variable alleles at a single locus.

Variable number of tandem repeat analysis using a ministatellite DNA probe pYNH24 to distinguish variable alleles at a single locus was applied to forensic analysis of DNA extracted from a murder and body abandonment specimen. Two bands detected by pYNH24 correspond to identical DNA from both the upper and lower halves of a separated body, suggesting that these halves were from the same body.

DNA Probes↗
PubMedDate not supplied

A guide to interpreting single locus profiles of DNA mixtures in forensic cases.

Analysis of a mixed body fluid crime sample by means of a single locus DNA probe may give rise to several bands. If a suspect is found to have a profile which matches two of the bands, then the evaluation of the evidential strength requires careful analysis. This paper describes the analysis of two relatively simple case examples. It is intended that the principles of the interpretative process will provide a guide to caseworkers who may encounter similar cases. The extension of the treatment to more complex cases should be clear.

Body Fluids↗
PubMed1992

Restriction fragment length polymorphism analysis of zoo animals using HaeIII and four single-locus probes.

Using HaeIII as the restriction endonuclease, restriction fragment length polymorphism analysis of dried blood samples from various animals was conducted. Single-locus probes D2S44, D10S28, D1S7, and D4S139, as well as monomorphic probe D7Z2, were used to examine for banding patterns. If bands were present, the samples were further examined for heterogeneity (whether single or multiple bands were observed) and polymorphism (whether variation in band location was shown between the animals studied within a species). Blood samples from animals, including primates, were obtained from Miami Metrozoo, Miami, Florida. Some of the animals were non-related individuals while others were related. Banding patterns were observed in colobus' for D2S44, D1S7, and D4S139; owl monkeys for D2S44; gorillas for D2S44 and D4S139; gibbons for D2S44 and D4S139; siamangs for D2S44, talapoins for DiS7; cranes for D1S7; and otters for D1S7. Based upon these, all of the animals for which a conclusion could be drawn appeared to be homozygous and monomorphic (exhibited only an invariant single band) for the loci examined except colobus' for D4S139, gorillas for D4S139, cranes for D1S7, and otters for D1S7.

Animals↗
PubMedDate not supplied

An efficient statistical procedure for interpreting DNA single locus profiling data in crime cases.

This paper describes a simplified approach to calculating the Bayesian likelihood ratio for the case where two DNA single locus profiles are to be compared. It explains how the calculation allows for band shift and also for the variation in precision with molecular weight. A simple basic theory section explains the principles of the analysis but more detailed explanations are given in an advanced theory section. Experiments on substantial data collections are described which demonstrate the robustness of the method.

Bayes Theorem↗
PubMed1977

Estimating the parameters of the incompletely penetrant single locus model using multiple populations.

A method involving the comparison of two or more populations is suggested as a means of obtaining a unique solution to the parameters of the incompletely penetrant single locus model. The proposed method allows a test of the assumptions of the model when three or more populations are compared. Equations that allow the inclusion of data on twin concordance rates and/or the proportion of affected children given neither, one or both parents affected are also given. Finally, some implications of fitting the model are discussed in terms of genetic counseling, residual environmental variance and the concept of heritability as applied to dichotomous traits.

Female↗
PubMed1992

The flax ribosomal RNA-encoding genes are arranged in tandem at a single locus interspersed by 'non-rDNA' sequences.

The ribosomal RNA (rRNA)-encoding genes (rDNA) in flax, estimated to be present in about 2400 copies per diploid nucleus, have been reported as a single homogeneous repeat unit of 8.6 kb. In situ hybridization analysis indicated that these genes were located at a single site on one pair of chromosomes. However, an analysis of a flax variety, CI 1303, has revealed heterogeneity in the intergenic spacer of the rDNA repeat unit. A genetic analysis of rDNA inheritance in two flax lines, Stormont Cirrus and CI 1303, has again supported the observation that there is a single rDNA locus in this plant species. Screening of four different genomic libraries made in methylation-sensitive and -insensitive systems, and the analysis of 40 phage clones, demonstrate a much higher number than that expected of junctions between rDNA and non-rDNA. Direct evidence of rRNA-encoding genes being present in tandem comes from a few phage clones that contain more than two rDNA repeats. The evidence presented here indicates that rDNA, although present at a single locus in tandem arrays, may be interrupted frequently by other non-rDNA sequences, thus giving rise to questions about their organization into long tandem arrays.

Blotting, Southern↗
PubMed1991

Population genetic data determined for five different single locus minisatellite probes.

We report on the population genetic data (frequencies of restriction fragments, heterozygosity rates, and mutation rates) obtained by analysis of approximately 1100 Hinfl-digested DNAs from West Germans. Probe G3 detects a common 1.7 kb DNA fragment showing a population frequency of about 13%. All the other fragments detected with probes MS1, MS31, MS43, G3 and YNH24 show frequencies of less than 8%. These data suggest that single locus DNA probes can provide valuable information for parentage evaluation and individualization.

DNA Probes↗
PubMed1991

Elucidation of apparent non-maternity with DNA probes detecting highly polymorphic single locus systems.

During paternity testing, we encountered the following constellation in the Jk system: the mother's phenotype was Jk(a-b+), while the son was typed as Jk(a+b-). The deduced genotype of the mother would have been Jkb Jkb, and each offspring should then express the Jk(b) antigen. Consequently, non-maternity would be deduced. Since no material was available for extended family studies or HLA typing, except for the DNA of the propositi, only RFLP analysis could bring clarification in this case. The application of four highly polymorphic single locus probes proved the maternity and hence the existence of a Jk-Null allele. We conclude that direct testing at the DNA level may help resolving cases where, by conventional parentage testing, conclusive results are unachievable because of putative 'Null' alleles.

Alleles↗